1. Field of the Invention
The present invention relates to a piezoelectric element including a piezoelectric layer made of a piezoelectric material, a method of manufacturing the same, and a liquid jet head including the same.
2. Description of the Related Art
A piezoelectric element is an element which interposes, between two electrodes, a piezoelectric film made of a piezoelectric material having electrical-mechanical conversion functions. The piezoelectric film is constituted of a crystallized piezoelectric ceramic, for example.
In addition, as a liquid jet head for which such piezoelectric elements are used, for example, there has been an ink-jet recording head as follows. With regard to the ink-jet recording head, parts of each of pressure generating chambers, which communicate respectively with nozzle orifices from which ink droplets are to be ejected, are composed of a vibration plate. This vibration plate is caused to be deformed by piezoelectric elements, thus pressurizing ink in a corresponding pressure generating chamber. Thereby, ink droplets are ejected from the nozzle orifices. For the ink-jet recording head, there have been two types which are put in practical use: one using a piezoelectric actuator of longitudinal vibration mode, which extends and contracts in the axial direction of the piezoelectric element; and the other using a piezoelectric actuator of flexure vibration mode. For ink-jet recording heads using the actuator of flexure vibration mode, there has been an ink-jet recording head having piezoelectric elements which are to be formed in the following process: for example, an even piezoelectric film is formed in the entire surface of the vibration plate by a deposition technique. Thereafter, the piezoelectric layer is cut into pieces, each of which has a shape corresponding to each of the pressure generating chambers by use of a lithography technique. Thus, piezoelectric elements are formed in a way that the piezoelectric elements in the respective pressure generating chambers are independent of one another.
For this piezoelectric layer (piezoelectric thin film) for example, a ferroelectric such as lead-zirconate-titanate (PZT) is used. In addition, such a piezoelectric thin film is formed in the following process: for example, titanium crystals are deposited on a lower electrode by use of a sputtering method or the like. Thereafter, a piezoelectric precursor film is formed on the titanium crystals by use of a sol-gel method. Then, this piezoelectric precursor film is baked, and accordingly, the piezoelectric thin film is formed (see Japanese Patent Laid-open Official Gazette No. 2001-274472, for example).
If the piezoelectric layer were formed in such a manner, crystals of the piezoelectric layer could be grown with crystals of titanium serving as nuclei. Accordingly, columnar crystals with relatively high density could be obtained. However, it is difficult to control the crystallinity of the piezoelectric layer, and it is impossible to homogenize electrical and mechanical characteristics of the piezoelectric layer. This brings about a problem that displacement characteristics of the respective piezoelectric elements are uneven.